Mechanical optics for mixed mode surgical laser illumination

ABSTRACT

Mechanical optics for mode mixing may be used to homogenize different modes in an optical fiber used for surgical illumination. A mechanical optical element, such as a rotating prism or a mirror membrane, may impart motion to an incident beam entering the optical fiber to generate a homogeneous illumination field from a coherent light source.

BACKGROUND Field of the Disclosure

The present disclosure relates to surgical illumination, and more specifically, to mechanical optics for mixed mode surgical laser illumination.

Description of the Related Art

In ophthalmology, eye surgery, or ophthalmic surgery, is performed on the eye and accessory visual structures. More specifically, vitreoretinal surgery encompasses various delicate procedures involving internal portions of the eye, such as the vitreous humor and the retina. Different vitreoretinal surgical procedures are used, sometimes with lasers, to improve visual sensory performance in the treatment of many eye diseases, including epimacular membranes, diabetic retinopathy, vitreous hemorrhage, macular hole, detached retina, and complications of cataract surgery, among others.

During vitreoretinal surgery, an ophthalmologist typically uses a surgical microscope to view the fundus through the cornea, while surgical instruments that penetrate the sclera may be introduced to perform any of a variety of different procedures. The patient typically lies supine under the surgical microscope during vitreoretinal surgery and a speculum is used to keep the eye exposed. Depending on a type of optical system used, the ophthalmologist has a given field of view of the fundus, which may vary from a narrow field of view to a wide field of view that can extend to peripheral regions of the fundus.

Additionally, an illumination source is typically introduced into the fundus to illuminate the area where the surgeon will be working. The illumination source is typically implemented as a surgical tool having an illuminator assembly that also penetrates the sclera and may be combined with other surgical tools. The use of optical fibers transmitting coherent light as illumination sources for surgery is desirable because of the high light intensity provided within very small physical dimensions available with optical fibers.

SUMMARY

The disclosed embodiments of the present disclosure provide mechanical optics for mode mixing to homogenize different modes in an optical fiber used for surgical illumination. A mechanical optical element, such as a rotating prism or a mirror membrane, may impart motion to an incident beam entering the optical fiber to generate a homogeneous illumination field from a coherent light source.

In one aspect, a disclosed method is for surgical illumination. The method may include projecting first light from a coherent light source into an optical fiber using a first condenser lens to direct the first light onto a mechanical optical element that redirects the first light to a focal spot at a fiber core of the optical fiber to generate second light, the second light used for illumination of a patient during a surgery. The method may further include causing the mechanical optical element to move the focal spot over the fiber core, and transmitting the second light from the optical fiber to a second optical fiber that projects the second light onto the patient.

In any of the disclosed embodiments of the method, the surgery may be an ophthalmic surgery, while the second optical fiber may project the second light into an eye of the patient. The method may further include measuring an intensity of the second light from the optical fiber. Based on the intensity measured, the method may include controlling the mechanical optical element to limit movement of the focal spot to the fiber core.

In any of the disclosed embodiments of the method, the coherent light source may be a monochromatic laser.

In any of the disclosed embodiments of the method, the coherent light source may be a plurality of monochromatic lasers combined to generate the first light.

In any of the disclosed embodiments of the method, the mechanical optical element may be a prism that deflects the first light, while the method operation of causing the mechanical optical element to move the focal spot may further include rotating the prism about an axis parallel to a transmission direction of the optical fiber, and focusing the second light using a second condenser lens onto the fiber core.

In any of the disclosed embodiments of the method, the method operation of causing the mechanical optical element to move the focal spot may further include, while the prism is rotating, vibrating the prism in a plane perpendicular to the transmission direction.

In any of the disclosed embodiments of the method, the prism may impart at least one of a reciprocal motion and a circular motion to the focal spot.

In any of the disclosed embodiments of the method, the mechanical optical element may be a mirror membrane that reflects the first light, while the method operation of causing the mechanical optical element to move the focal spot may further include perturbing the mirror membrane.

In any of the disclosed embodiments of the method, perturbing the mirror membrane may impart a randomized motion to the focal spot.

In any of the disclosed embodiments of the method, the coherent light source may be a third optical fiber receiving the first light from a laser, while the mechanical optical element is included in a mechanical mode mixer device that may further include an input optical connector for connection to the third optical fiber, an output optical connector for connection to the optical fiber, and a power source to power the mechanical optical element.

In a further aspect, a disclosed device is for surgical illumination. The device may include a coherent light source for generating first light. The device may further include a condenser lens for focusing the first light onto a mechanical optical element that redirects the first light to a focal spot at a fiber core of an optical fiber to generate second light, the second light used for illumination of a patient during a surgery. The device may also include the mechanical optical element and a mechanical actuator for moving the mechanical optical element, such that the focal spot is moved over the fiber core to generate second light, and a second optical fiber receiving the second light from the optical fiber, the second optical fiber projecting the second light onto the patient.

In any of the disclosed embodiments of the device, the surgery may be an ophthalmic surgery, while the second optical fiber may project the second light into an eye of the patient. The device may further include an optical intensity sensor to measure an intensity of the second light from the optical fiber. In the device, the mechanical optical element may be controlled based on the intensity measured to limit movement of the focal spot to the fiber core.

In any of the disclosed embodiments of the device, the coherent light source may be a monochromatic laser.

In any of the disclosed embodiments of the device, the coherent light source may be a plurality of monochromatic lasers combined to generate the first light.

In any of the disclosed embodiments of the device, the mechanical optical element may be a prism that deflects the first light, while the mechanical actuator may rotate the prism about an axis parallel to a transmission direction of the optical fiber, and while second light from the prism is focused onto the fiber core using a second condenser lens.

In any of the disclosed embodiments of the device, the mechanical actuator, while the prism is rotating, may further vibrate the prism in a plane perpendicular to the transmission direction.

In any of the disclosed embodiments of the device, the prism may impart at least one of a reciprocal motion and a circular motion to the focal spot.

In any of the disclosed embodiments of the device, the mechanical optical element may be a mirror membrane that reflects the first light, while the mechanical actuator may perturb the mirror membrane.

In any of the disclosed embodiments of the device, the mechanical actuator may impart a randomized motion to the focal spot.

In any of the disclosed embodiments of the device, the coherent light source may be a third optical fiber receiving the first light from a laser, while the mechanical optical element may be included in a mechanical mode mixer device that may further include an input optical connector for connection to the third optical fiber, an output optical connector for connection to the optical fiber, and a power source to power the mechanical optical element.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure and its features and advantages, reference is now made to the following description, taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a depiction of an embodiment of an ophthalmic surgery using a surgical microscope and a surgical tool with an illuminator assembly;

FIG. 2 is an image of inhomogeneous light from fiber modes;

FIG. 3 is a depiction of an embodiment of a surgical illumination system with mechanical optics for mode mixing;

FIG. 4A is a depiction of an embodiment of a light source with a rotating prism;

FIG. 4B is a depiction of an embodiment of a light source with a mirror membrane;

FIG. 4C is a depiction of an embodiment of a secondary mechanical optic device;

FIG. 4D is a depiction of an embodiment of a mechanical mode mixer device with a rotating prism;

FIG. 4E is a depiction of an embodiment of a mechanical mode mixer device with a mirror membrane; and

FIG. 5 is a flow chart of selected elements of a method for surgical laser illumination.

DESCRIPTION OF PARTICULAR EMBODIMENT(S)

In the following description, details are set forth by way of example to facilitate discussion of the disclosed subject matter. It should be apparent to a person of ordinary skill in the field, however, that the disclosed embodiments are exemplary and not exhaustive of all possible embodiments.

As used herein, a hyphenated form of a reference numeral refers to a specific instance of an element and the un-hyphenated form of the reference numeral refers to the collective element. Thus, for example, device ‘12-1’ refers to an instance of a device class, which may be referred to collectively as devices ‘12’ and any one of which may be referred to generically as a device ‘12’.

As noted above, the use of optical fibers and coherent light sources is desirable for surgical illumination because of the high light intensity provided within the very small physical dimensions of an optical fiber. Although such surgical illumination sources may be used in various medical and surgical applications, one exemplary application is in eye surgery, such as for vitreoretinal surgery.

For vitreoretinal surgery, for example, the illumination source is typically implemented as a surgical tool having an illuminator assembly that penetrates the sclera and may be combined with other surgical tools. At a distal end of the illuminator assembly, a very small diameter optical fiber may be used to project light into the fundus to illuminate surgical procedures performed within the eye. The very small diameter fiber, for example having a fiber core of about 25-100 μm, is typically coupled to an optical fiber that couples proximally to a coherent light source, such as a laser source. Although various types of optical fibers may be used, multi-mode optical fibers may be used to transmit coherent light into the eye for illumination.

However, as coherent light is transmitted through a multi-mode optical fiber, different groups of photons of the coherent light, referred to as “modes”, within the fiber may traverse slightly different path lengths. As a result of the different path lengths experienced by different modes within the optical fiber, the modes may constructively and destructively interfere with each other during propagation within the optical fiber. As the different modes exit the optical fiber from a fiber core, an illumination field provided by the exiting light may appear inhomogeneous due to the inter-mode interference. The inter-mode interference may be highly sensitive to temperature, fiber strain, fiber motion, and may generally become quite noticeable to the human eye, since the inhomogeneous illumination field projects an undesired dynamic pattern, instead of a homogeneous illumination field projecting uniform background light. Because the inhomogeneous illumination field appears as different regions of different colored light that may be dynamic, the inhomogeneous illumination field may be poorly suited for surgical illumination.

For example, in vitreoretinal surgery, a clear and unambiguous view of various fine biostructures in the eye is highly desirable to enable a surgeon to operate safely and effectively, which the inhomogeneous illumination field may not provide. In particular, the inhomogeneous illumination field is observed with monochromatic laser sources, or combinations of monochromatic laser sources in some implementations. The monochromatic laser sources may exhibit fewer modes and, thus, a lesser degree of mode mixing within the optical fiber that enables homogenization of the coherent light into a desired homogeneous illumination field. Furthermore, as various surgical tools are designed and implemented, such as endoilluminators or surgical tools with combined illumination, the use of smaller fiber diameters carrying high light intensity becomes increasingly desirable. However, the inter-mode interference issues become increasingly exacerbated as the size (i.e., diameter) of an optical fiber decreases, which may undesirably constrain the use of such compact illumination systems. Also, in surgical illumination applications, a relatively short length of optical fiber is used, such as about 2-3 m in length. Because mode mixing that leads to a more homogeneous illumination field increases with fiber length, shorter optical fibers used in in surgical illumination applications may experience insufficient mode mixing that results in the inhomogeneous illumination field. Also, optical fibers comprised of a glass core may exhibit fewer modes and less mode mixing, and may be particularly subject to the inhomogeneous illumination field.

As will be described in further detail, mechanical optics for mixed mode surgical laser illumination are disclosed. The mechanical optics for mixed mode surgical laser illumination disclosed herein may provide a homogeneous illumination field for surgical illumination using optical fibers to transmit coherent light. The mechanical optics for mixed mode surgical laser illumination disclosed herein may be used with relatively short and relatively small diameter optical fibers. The mechanical optics for mixed mode surgical laser illumination disclosed herein may be used with optical fibers having a glass core. The mechanical optics for mixed mode surgical laser illumination disclosed herein may be implemented at a light source for surgical illumination. The mechanical optics for mixed mode surgical laser illumination disclosed herein may be implemented as an optical device that can be coupled to an optical fiber providing surgical illumination from a coherent light source. The mechanical optics for mixed mode surgical laser illumination disclosed herein may be used for illumination of a patient's eye during ophthalmic surgery, such as vitreoretinal surgery.

One manner in which an illumination assembly 100 may be used is illustrated in FIG. 1, in which a surgeon 120 is performing an ophthalmic surgery on an eye 104 of a patient 130 using a surgical tool 122. In FIG. 1, the eye 104 has been exposed using a speculum 140 and a contact lens 150 is held in place on the eye 104 and visually aligned with a surgical microscope 102 to facilitate visualization of inner structures of the eye 104. The surgeon 120 is using the surgical tool 122 to perform surgery on inner structures of the eye 104.

For example, when the surgical tool 122 is a vitrectomy probe, then the surgeon 120 may be using the surgical tool 122 to remove the clear, gel-like vitreous that normally fills the interior of the eye 104, taking care to remove substantially only the vitreous, while avoiding interaction with nearby eye structures, such as the retina, that are extremely sensitive to any mechanical action. The ability of the surgeon to clearly view the fundus is facilitated by a homogenous illumination field that is provided by illumination assembly 100. It is noted that surgical tool 122 may by any of a variety of handheld surgical tools. In some embodiments, illumination assembly 100 may be integrated within surgical tool 122 to provide illumination without having to use a secondary illumination tool.

In the inset of FIG. 1, additional details of the eye 104 during surgery are shown. Two scleral ports 108 for providing cannulated scleral penetration are visible, one for surgical tool 122 and one for illuminator assembly 100. As shown, illuminator assembly 100 may include mechanical optics for mixed mode surgical laser illumination, as described in further detail below. Accordingly, illuminator assembly 100 may be used to project coherent light into the eye 104 using an optical fiber to transmit the light to project a homogenous illumination field (not visible in FIG. 1) into the fundus.

Modifications, additions, or omissions may be made to illuminator assembly 100 without departing from the scope of the disclosure. The components and elements of surgical illuminator assembly 100, as described herein, may be integrated or separated according to particular applications. Illuminator assembly 100 may be implemented using more, fewer, or different components in some embodiments.

FIG. 2 illustrates an image 200 of inhomogeneous light from fiber modes. Image 200 depicts coherent light from an optical fiber projected onto a screen that is oriented oblique to the page. In image 200, the depicted screen has extraneous annotations written in black ink above and below an inhomogeneous illumination field. The inhomogeneous illumination field in image 200 results from insufficient mode mixing within the optical fiber. The inhomogeneous illumination field in image 200 may exhibit intensity variations up to about 500%, which may be dynamic in many applications and usage scenarios, which is undesirable for surgical illumination, as explained previously. The inhomogeneous illumination field in image 200 may be immediately converted into a homogeneous illumination field, such as a substantially uniform intensity illumination field (not shown) by applying the techniques for mode mixing disclosed herein.

Referring now to FIG. 3, a depiction of an embodiment of a surgical illumination system 300 is shown. As shown in FIG. 3, surgical illumination system 300 may be used in the ophthalmic surgery on the eye 104 shown in FIG. 1. FIG. 3 is a schematic illustration and is not drawn to scale or perspective. In FIG. 3, a cross-sectional view of the eye 104 is shown, enabling a view of various elements described above with respect to FIG. 1. Specifically, contact lens 120 is shown providing a relatively wide angle view of the fundus of the eye 104, while two scleral ports 108 penetrate the sclera of the eye 104. A surgical tool 122 is shown penetrating one scleral port 108, while illumination assembly penetrates another scleral port 108.

As shown in FIG. 3, a homogeneous illumination field 310 is projected into the eye 104 by illuminator assembly 100. Specifically, illuminator assembly 100 terminates distally with an optical fiber portion 308, which may be exposed to project light into the eye. Optical fiber portion 308 is coupled to an external optical fiber 304. In some embodiments, optical fiber portion 308 may be a distal portion of external optical fiber 304 itself. Optical fiber 304 is shown passing through a hand piece 306, which may include a sheath or tube around optical fiber 304 to enable cannulation at scleral port 108. Optical fiber 304 is shown extending from a surgical console 312 to hand piece 306.

In FIG. 3, surgical console 312 may include mechanical optics for mixed mode surgical laser illumination, as disclosed herein. In some embodiments, the mechanical optics for mixed mode surgical laser illumination may be implemented as a separate device (see FIGS. 4C and 4D). Specifically, surgical console 312 may include a light source comprised of a laser source and a condenser lens (or equivalent optical element). The condenser lens may focus first light generated by the laser source onto a focal spot at mechanical optic, such as a rotating prism or a mirror membrane, that is electronically controlled. The mechanical optic may redirect the received light towards a fiber core of optical fiber 304 at a proximal end. The mechanical optic may be a rotating prism or a mirror membrane. In this manner, the focal spot is moved over the fiber core to generate second light that is transmitted by optical fiber 304. Because movement of the focal spot creates or enhances mode mixing in optical fiber 304, the second light may provide a homogeneous illumination field 310 in the eye 104 after exiting optical fiber portion 308, which is at a distal end of optical fiber 304.

Surgical console 312 may provide various other equipment and functionality, such as driver equipment for surgical tool 122, and a user interface for data operations and image processing. Further internal details of the mechanical optics for mixed mode surgical laser illumination are described below with respect to FIGS. 4A, 4B, 4C, 4D and 4E-.

Referring now to FIG. 4A, a depiction of an embodiment of a light source 400-1 with a rotating prism 433-1 is shown. FIG. 4A is a schematic illustration and is not drawn to scale or perspective. In FIG. 4A, elements included within light source 400-1 are shown schematically from a side view. It will be understood that light source 400 may be implemented as an optical device, for example having an enclosure (not shown) to house the components illustrated in FIG. 4A. In particular embodiments, light source 400-1 may be included with or integrated with surgical console 312 (see FIG. 3), where optical fiber 304 may begin at a proximal end.

In light source 400-1, a laser source 430 may represent a source of coherent light. Laser source 430 may represent a monochromatic light source. Laser source 430 may represent a combination of a plurality of monochromatic light sources, in some embodiments. Laser source 430 may generate first light 440-1, which is coherent light. First light 440-1 may be projected onto a first condenser lens 432-1, which may be used to focus first light 440-1 onto a rotating prism 434-1 mounted on a prism assembly 433. Rotating prism 433-1 may direct the first light 440-1 onto a second condenser lens 432-2 to generate second light 440-2, which focuses second light 440-2 at a fiber core 442 of optical fiber 304. First light 440-1 may be generated as a collimated laser beam of about 1-5 mm in diameter having an optical power in the range of about 10-500 mW in various embodiments. First light 440-1 may be focused onto a focal spot that is about 5-10 μm in diameter by condenser lens 432. The focal spot may be less than 20 μm in diameter, or less than 25 μm in diameter in various embodiments. Fiber core 442 may be as small as about 30 μm in diameter. In some embodiments, fiber core 442 may about 50 μm in diameter, or about 100 μm in diameter, or various diameter sizes therebetween.

Additionally, in light source 400-1, laser source 430, optical fiber 304, and a prism stage 434 are shown situated on a fixed surface 436, which may represent a base of a housing (not shown) which may enclose light source 400-1. In some embodiments, fixed surface 436 is included in surgical console 312. Laser source 430 and optical fiber 304 are fixed by supports 438, which may represent any type of mechanical attachment to hold laser source 430 and optical fiber 304 in a fixed position relative to first condenser lens 432-1, prism assembly 433, and second condenser lens 432-2 as depicted. First condenser lens 432-1 and second condenser lens 432-2 are also assumed to be in a fixed position in FIG. 4A.

As shown in FIG. 4A, prism assembly 433 may be a mounting plate with a central opening (not visible) through which first condenser lens 432-1 focuses first light 440-1 onto rotating prism 433-1, which is mounted centrally on prism assembly 433. Prism assembly 433 may be enabled to rotate, such as with a belt drive and corresponding bearings, about a central axis 446 that is parallel with a central axis of optical fiber 304. Arrow 435 depicts a circular direction of rotation of rotating prism 433-1 that is perpendicular to central axis 446 and indicates the motion of second light 440-2 as second light 440-2 is projected onto a fiber core 442. Also shown is prism stage 434, which may represent mechanical components to drive and support prism assembly 433, such as a motor and supporting members, and enable prism assembly 433 to spin, along with rotating prism 433-1. It is noted that the angular motion of rotating prism 433-1 may be a regular circular motion, or may be a more irregular motion, such as by reversing direction, or motion over a specific angular range. Accordingly, prism stage 434 may include various types of motors or drives, including stepper motors, to enable the motion of prism assembly 433.

In FIG. 4A, rotating prism 433-1 may be made of a suitable material and shaped to deflect a certain wavelength of light, such as a wavelength of light included in first light 440-1. In particular, rotating prism 433-1 may be designed for a deflection radius of second light 440-2 that is at least as small as a radius of fiber core 442. It is noted that rotating prism 433-1 having a smaller deflection radius of second light 440-2 than the radius of fiber core 442 may still be useful for mechanical mode mixing, as disclosed herein.

In various embodiments, additional axis of motion of second light 440-2 may be enabled by prism assembly 433. For example, when prism assembly 433 includes a dual axis piezoelectric stage (not shown) on which rotating prism 433-1 is mounted, lateral motion in a plane perpendicular to the page of FIG. 4A may additionally be imparted to rotating prism 433-1. In this manner, second light 440-2 may be directed in any arbitrary two-dimensional pattern or path over fiber core 442.

Although prism assembly 433 is shown in an upright orientation for descriptive clarity in FIG. 4A, it is noted that light source 400-1 may be implemented using any orientation or alignment of prism assembly 433 to optical fiber 304 that enables rotation of second light 440-2 over fiber core 442, as indicated by arrow 435. Accordingly, rotating prism 433-1 may impart at least one of a reciprocal motion and a circular motion to second light 440-2. In some embodiments, rotating prism 433-1 may impart a randomized motion to second light 440-2. In different embodiments, rotating prism 433-1 may cause second light 440-2 to reciprocate, rotate, or oscillate at a frequency to cause motion that is not visible to the human eye, such as at a frequency of about 30 Hz or greater.

Referring now to FIG. 4B, a depiction of an embodiment of a light source 400-2 with mechanical optics comprising a mirror membrane 444 is shown. FIG. 4B is a schematic illustration that includes similar elements as FIG. 4A and is not drawn to scale or perspective. In FIG. 4B, elements included within light source 400-2 are shown schematically from a top view. The arrangement of mirror membrane 444 enables mirror membrane 444 to operate in reflection. It will be understood that light source 400-2 may be implemented as an optical device, for example having an enclosure (not shown) to house the components illustrated in FIG. 4B. In particular embodiments, light source 400-2 may be included with or integrated with surgical console 312 (see FIG. 3), where optical fiber 304 may begin at a proximal end.

In FIG. 4B, mirror membrane 444 may be comprised of a thin, flexible membrane that is reflective on one surface. Mirror membrane 444 may be controlled using a mechanical actuator, such as by perturbing mirror membrane 444, to vary its shape slightly, thereby causing second light 440-2 reflected from mirror membrane 444 and focused by second condenser lens 432-2 towards fiber core 442 to be slightly deflected. When the mechanical actuator imparts a vibration or an oscillation to mirror membrane 444, a corresponding vibration or oscillation of second light 440-2 at fiber core 442 will occur. In this manner, the movement of second light 440-2 projected onto fiber core 442 may be controlled and may result in mode mixing within optical fiber 304. In different embodiments, mirror membrane 444 may cause second light 440-2 to reciprocate, vibrate, or oscillate at a frequency to cause motion that is not visible to the human eye, such as at a frequency of about 30 Hz or greater.

Referring now to FIG. 4C, a depiction of an embodiment of a secondary mechanical optic device 401 is shown. FIG. 4C is a schematic illustration and is not drawn to scale or perspective. In FIG. 4C, elements included within secondary mechanical optic device 401 are shown schematically. It will be understood that secondary mechanical optic device 401 may be implemented as an optical device, for example having an enclosure (not shown) to house the components illustrated in FIG. 4C. In particular embodiments, secondary mechanical optic device 401 may be installed along optical fiber 304 as an intermediate optical device, while optical fiber 304 may be implemented in two sections with the appropriate optical connectors.

Specifically, secondary mechanical optic device 401 is shown having input optical connector 402 for connecting to optical fiber 304-1, as well as having output optical connector 406 for connecting to optical fiber 304-2. In various embodiments, input optical connector 402 and output optical connector 406 may be releasable connectors (not shown) that mate with corresponding connectors attached to optical fibers 304-1 and 304-2. In some embodiments, input optical connector 402 and output optical connector 406 may be fixed connectors. As shown, input optical connector 402 couples to a first internal optical fiber 408-1 that connects to a mechanical mode mixer device 404. Mechanical mode mixer device 404 may connect to output optical connector 406 using a second internal optical fiber 408-2.

In secondary mechanical optic device 401, input optical connector 402 may receive first light 420-1, which may experience insufficient mode mixing in optical fiber 304-1 after being transmitted from a coherent light source. The coherent light source may be a monochromatic laser, or a combination of monochromatic lasers that have been combined to generate first light 420-1. Accordingly, first light 420-1 may include light from different frequencies (i.e., colors). First light 420-1 is transmitted by first internal optical fiber 408-1 to mechanical mode mixer device 404, which is similar to light source 400, and is described in further detail below with respect to FIGS. 4D and 4E. Mechanical mode mixer device 404 may output second light 420-2 that has been mode mixed to second internal optical fiber 408-2, which connects to output optical connector 406.

As shown in FIG. 4C, an optical tap 412 may be used along second internal optical fiber 408-2 to divert some optical energy from second light 420-2 to a photodiode 414 (or another optical intensity sensor). A feedback control signal 416 from photodiode 414 may be used by mechanical mode mixer device 404 to regulate the operation of mechanical mode mixer device 404, such that second light 440-2 remains directed at fiber core 442. When the second light 440-2 is not directed at fiber core 442, the intensity measured by photodiode 414 will decrease (assuming constant optical power at the coherent light source). In this manner, feedback control signal 416 may enable regulation of the operation of mechanical mode mixer 404 in a desired manner.

Also shown with secondary mechanical optic device 401 in FIG. 4C is power source 410, which may provide power to mechanical mode mixer device 404. In some embodiments, power source 410 may represent an internal power source to secondary mechanical optic device 401, such as a battery to enable remote operation. In other embodiments, power source 410 may represent an external power source, such as a connector for line power or direct current from an external power supply (not shown).

Referring now to FIG. 4D, a depiction of an embodiment of a mechanical mode mixer device 404-1 with a rotating prism 433-1 (see also FIG. 4A) is shown. FIG. 4D is a schematic illustration and is not drawn to scale or perspective. In FIG. 4D, elements included within mechanical mode mixer device 404-1 are shown schematically. It will be understood that mechanical mode mixer device 404-1 may be implemented as an optical device, for example having an enclosure (not shown) to house the components illustrated in FIG. 4D. In particular embodiments, mechanical mode mixer device 404-1 may be included with secondary mechanical optic device 401 described above.

In mechanical mode mixer device 404-1, first light 440-1 arrives from first internal optical fiber 408-1, as described previously. First light 440-1 may be condensed using condenser lens 432, as described previously. First light 440-1 may be redirected by rotating prism 433-1 mounted to prism assembly 433, which, as described above with respect to FIG. 4A, may be used to redirect first light 440-1 to generate second light 440-2 that is focused by second condenser lens 432-2 onto a fiber core 442 of second internal optical fiber 408-2. Prism assembly 433, driven by prism stage 434, may operate to impart vibration, motion, rotation, or translation to first light 440-1, such as indicated by arrow 435, as described previously, in various embodiments. Prism stage 434 is shown receiving feedback control signal 416 as an input for regulation of the redirection of first light 440-1, as described previously.

Additionally, in mechanical mode mixer device 404-1, optical fibers 408-1 and 408-2, along with a prism stage 434 are shown situated on a fixed surface 436, which may represent a base of a housing (not shown) which may enclose mechanical mode mixer device 404-1. Prism stage 434 and optical fibers 408-1 and 408-2 are fixed by supports 438, which may represent any type of mechanical attachment to hold prism stage 434 and optical fibers 408-1 and 408-2 fixed relative to prism assembly 433. In FIG. 4D it is assumed that first condenser lens 432-1 and second condenser lens 432-2 are also held in a fixed position.

Referring now to FIG. 4E, a depiction of an embodiment of a mechanical mode mixer device 404-2 with a mirror membrane 444 (see also FIG. 4B) is shown. FIG. 4E is a schematic illustration and is not drawn to scale or perspective. In FIG. 4E, elements included within mechanical mode mixer device 404-2 are shown schematically from a top view. The arrangement of mirror membrane 444 enables mirror membrane 444 to operate in reflection. It will be understood that mechanical mode mixer device 404-2 may be implemented as an optical device, for example having an enclosure (not shown) to house the components illustrated in FIG. 4E. In particular embodiments, mechanical mode mixer device 404-2 may be included with secondary mechanical optic device 401 described above.

In mechanical mode mixer device 404-2, first light 440-1 arrives from first internal optical fiber 408-1, as described previously. In FIG. 4E, mirror membrane 444 may be comprised of a thin, flexible membrane that is reflective on one surface. Mirror membrane 444 may be controlled using a mechanical actuator, such as by perturbing mirror membrane 444, to vary its shape slightly, thereby causing second light 440-2 reflected from mirror membrane 444 to be slightly deflected. Mirror membrane is shown reflecting second light 440-2 towards second condenser lens 432-2, which focuses second light 440-2 at a fiber core (not visible in FIG. 4E) of second internal optical fiber 408-2 When the mechanical actuator imparts a vibration or an oscillation to mirror membrane 444, a corresponding vibration or oscillation of second light 440-2 at the fiber core of second internal optical fiber 408-2 will occur. In this manner, the movement of second light 440-2 projected onto second internal optical fiber 408-2 may be controlled and may result in mode mixing within second internal optical fiber 408-2. In different embodiments, mirror membrane 444 may cause second light 440-2 to reciprocate, vibrate, or oscillate at a frequency to cause motion that is not visible to the human eye, such as at a frequency of about 30 Hz or greater.

Referring now to FIG. 5, a flow chart of selected elements of an embodiment of a method 500 for surgical laser illumination using mechanical optics for mode mixing, as described herein, is depicted in flowchart form. It is noted that certain operations described in method 500 may be optional or may be rearranged in different embodiments. Method 500 may be performed using illumination assembly 100, along with light source 400 or secondary mechanical optic device 401, as described herein.

Method 500 may begin, at step 502, by projecting first light from a coherent light source into an optical fiber using a condenser lens to direct the first light onto a mechanical optical element that redirects the first light to a focal spot at a fiber core of the optical fiber to generate second light, the second light used for illumination of a patient during a surgery. At step 504, the mechanical optical element is caused to move the focal spot over the fiber core. As disclosed herein, the mechanical optical element may be a rotating prism or a mirror membrane. At step 506, the second light is transmitted from the optical fiber to a second optical fiber that projects the second light onto the patient.

As disclosed herein, mechanical optics for mode mixing may be used to homogenize different modes in an optical fiber used for surgical illumination. A mechanical optical element, such as a rotating prism or a mirror membrane, may impart motion to an incident beam entering the optical fiber to generate a homogeneous illumination field from a coherent light source.

The above disclosed subject matter is to be considered illustrative, and not restrictive, and the appended claims are intended to cover all such modifications, enhancements, and other embodiments which fall within the true spirit and scope of the present disclosure. Thus, to the maximum extent allowed by law, the scope of the present disclosure is to be determined by the broadest permissible interpretation of the following claims and their equivalents, and shall not be restricted or limited by the foregoing detailed description. 

What is claimed is:
 1. A method for surgical illumination, the method comprising: projecting first light from a coherent light source into an optical fiber using a first condenser lens to direct the first light onto a mechanical optical element that redirects the first light to a focal spot at a fiber core of the optical fiber to generate second light, the second light used for illumination of a patient during a surgery; causing the mechanical optical element to move the focal spot over the fiber core; and transmitting the second light from the optical fiber to a second optical fiber that projects the second light onto the patient.
 2. The method of claim 1, wherein the surgery is an ophthalmic surgery, and the second optical fiber projects the second light into an eye of the patient, and further comprising: measuring an intensity of the second light from the optical fiber; based on the intensity measured, controlling the mechanical optical element to limit movement of the focal spot to the fiber core.
 3. The method of claim 1, wherein the coherent light source is a monochromatic laser.
 4. The method of claim 1, wherein the coherent light source is a plurality of monochromatic lasers combined to generate the first light.
 5. The method of claim 1, wherein the mechanical optical element is a prism that deflects the first light, and wherein causing the mechanical optical element to move the focal spot further comprises: rotating the prism about an axis parallel to a transmission direction of the optical fiber and focusing the second light using a second condenser lens onto the fiber core.
 6. The method of claim 5, wherein causing the mechanical optical element to move the focal spot further comprises: while the prism is rotating, vibrating the prism in a plane perpendicular to the transmission direction.
 7. The method of claim 6, wherein the prism imparts at least one of a reciprocal motion and a circular motion to the focal spot.
 8. The method of claim 1, wherein the mechanical optical element is a mirror membrane that reflects the first light, and wherein causing the mechanical optical element to move the focal spot further comprises: perturbing the mirror membrane.
 9. The method of claim 8, wherein perturbing the mirror membrane imparts a randomized motion to the focal spot.
 10. The method of claim 1, wherein the coherent light source is a third optical fiber receiving the first light from a laser, and wherein the mechanical optical element is included in a mechanical mode mixer device further comprising: an input optical connector for connection to the third optical fiber; an output optical connector for connection to the optical fiber; and a power source to power the mechanical optical element.
 11. A device for surgical illumination, the device comprising: a coherent light source for generating first light; a first condenser lens for focusing the first light onto a mechanical optical element that redirects the first light to a focal spot at a fiber core of an optical fiber to generate second light, the second light used for illumination of a patient during a surgery; the mechanical optical element; a mechanical actuator for moving the mechanical optical element, wherein the focal spot is moved over the fiber core; and a second optical fiber receiving the second light from the optical fiber, the second optical fiber projecting the second light onto the patient.
 12. The device of claim 11, wherein the surgery is an ophthalmic surgery, and the second optical fiber projects the second light into an eye of the patient, and further comprising: an optical intensity sensor to measure an intensity of the second light from the optical fiber, wherein the mechanical optical element is controlled based on the intensity measured to limit movement of the focal spot to the fiber core.
 13. The device of claim 11, wherein the coherent light source is a monochromatic laser.
 14. The device of claim 11, wherein the coherent light source is a plurality of monochromatic lasers combined to generate the first light.
 15. The device of claim 11, wherein the mechanical optical element is a prism that deflects the first light, wherein the mechanical actuator rotates the prism about an axis parallel to a transmission direction of the optical fiber, and wherein second light from the prism is focused onto the fiber core using a second condenser lens.
 16. The device of claim 15, wherein the mechanical actuator, while the prism is rotating, further vibrates the prism in a plane perpendicular to the transmission direction.
 17. The device of claim 16, wherein the prism imparts at least one of a reciprocal motion and a circular motion to the focal spot.
 18. The device of claim 11, wherein the mechanical optical element is a mirror membrane that reflects the first light, and wherein the mechanical actuator perturbs the mirror membrane.
 19. The device of claim 18, wherein the mechanical actuator imparts a randomized motion to the focal spot.
 20. The device of claim 11, wherein the coherent light source is a third optical fiber receiving the first light from a laser, and wherein the mechanical optical element is included in a mechanical mode mixer device further comprising: an input optical connector for connection to the third optical fiber; an output optical connector for connection to the optical fiber; and a power source to power the mechanical optical element. 